diff --git a/lib/messages.js b/lib/messages.js
index bb1ebd9..c821c27 100644
--- a/lib/messages.js
+++ b/lib/messages.js
@@ -836,7 +836,7 @@ module.exports.GetHeaders = Message.COMMANDS.getheaders = GetHeaders;
  */
 function FilterLoad(filter) {
   this.command = 'filterload';
-  $.checkArgument(_.isUndefined() || filter instanceof BloomFilter,
+  $.checkArgument(_.isUndefined(filter) || filter instanceof BloomFilter,
     'BloomFilter object  or undefined required for FilterLoad');
   this.filter = filter;
   return this;